Module expect/mod

This module provides Jest compatible expect assertion functionality.

import { expect } from "@std/expect";

const x = 6 * 7;
expect(x).toEqual(42);
expect(x).not.toEqual(0);

await expect(Promise.resolve(x)).resolves.toEqual(42);
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Currently this module supports the following functions:

• Common matchers:
  • toBe
  • toEqual
  • toStrictEqual
  • toMatch
  • toMatchObject
  • toBeDefined
  • toBeUndefined
  • toBeNull
  • toBeNaN
  • toBeTruthy
  • toBeFalsy
  • toContain
  • toContainEqual
  • toHaveLength
  • toBeGreaterThan
  • toBeGreaterThanOrEqual
  • toBeLessThan
  • toBeLessThanOrEqual
  • toBeCloseTo
  • toBeInstanceOf
  • toThrow
  • toHaveProperty
• Mock related matchers:
  • toHaveBeenCalled
  • toHaveBeenCalledTimes
  • toHaveBeenCalledWith
  • toHaveBeenLastCalledWith
  • toHaveBeenNthCalledWith
  • toHaveReturned
  • toHaveReturnedTimes
  • toHaveReturnedWith
  • toHaveLastReturnedWith
  • toHaveNthReturnedWith
• Asymmetric matchers:
  • expect.anything
  • expect.any
  • expect.arrayContaining
  • expect.not.arrayContaining
  • expect.objectContaining
  • expect.not.objectContaining
  • expect.closeTo
  • expect.stringContaining
  • expect.not.stringContaining
  • expect.stringMatching
  • expect.not.stringMatching
• Utilities:
  • expect.addSnapshotSerializer
  • expect.assertions
  • expect.addEqualityTester
  • expect.extend
  • expect.hasAssertions

Only these functions are still not available:

• Matchers:
  • toMatchSnapshot
  • toMatchInlineSnapshot
  • toThrowErrorMatchingSnapshot
  • toThrowErrorMatchingInlineSnapshot

The tracking issue to add support for unsupported parts of the API is https://github.com/denoland/std/issues/3964.

This module is largely inspired by x/expect module by Allain Lalonde.